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Corrosion Control

Corrosion Control is a serious concern for all manufacturers, especially those using a "closed-loop" cooling system for injection molds. The microstructure and heat treatment of tool steels are carefully controlled to optimize corrosion resistance. The joining of dissimilar metals presents a never-ending battle with corrosion.

Terminology

The following terms relate to Corrosion Control:

Alloy

A substance that has metallic properties and is composed of two or more chemical elements of which at least one is a metal.

Corrosion

The deterioration of a metal by chemical and/or electrochemical reaction with its environment. Surface oxidation is a common form of corrosion.

Corrosion Embrittlement

The embrittlement caused in certain alloys that are susceptible to intergranular corrosion attack when they are exposed to a corrosive environment.

Corrosion Resistance

The ability of some metals to form a protective oxide or passive layer which renders them more resistant to corrosion.

Intergranular Corrosion

A type of galvanic corrosion that progresses along the grain boundaries of an alloy. The grain boundaries become anodic to the grains and deteriorate, usually causing failure of the part.

Oxidation

(1) Surface oxidation of a metal caused by thermal exposure in air. (2) A reaction in which there is an increase in valence resulting from a loss of electrons. (3)A corrosion reaction in which the metal combines with oxygen to form an oxide. In steels, an oxidized surface is manifest by discoloration from a straw to a dark blue/black brittle and flaky scale.